In pumping applications, it is sometimes desirable to operate two centrifugal pumps in parallel. In the aircraft industry it is desirable for single engine aircraft where safety requirements demand that two fuel pumps operate in parallel so that if one pump fails, the other one will continue to supply fuel to the engine. Centrifugal pumps have characteristics that do not allow them to operate in parallel at low flows without additional means. Centrifugal pumps are capable of operating in parallel at higher flows. However, aircraft fuel pumps must operate over a wide range of flows and if they are simply hooked together, all of the demand at low flows will be supplied out of one pump while the other pump will be back flowed by the higher pressure of the other pump.